This invention relates generally to radio-frequency mixers, and more particularly to low voltage, highly linear, double balanced radio-frequency mixers for wireless applications.
Wireless devices are widely used. Wireless devices eliminate a cable or wire that would otherwise be needed. Wireless devices provide great benefits to users such as portability and ease of use. Wireless devices, such devices as cellular phones, radios, television, and cordless phones, are widely used and provide great benefits to users such as portability and ease of use. In addition, wireless devices eliminate a physical communication line, such as a cable or wire, that would otherwise be needed to carry the communicated data.
Many wireless devices utilize radio frequencies (RF) or infra red to transmit and receive data via wireless communication. A device transmits information by using radio frequencies and another device or devices receive that information by detecting and using RF. The transmitting device can also be a receiver. The transmitting device, among other operations, shifts the information signal from baseband frequencies to RF frequencies where it will experience more efficient transmission through the antenna. The receiving device, among other operations, shifts the RF signal from the antenna to lower frequencies, where demodulation and detection take place. The receiving device can then utilize the signal for a desired purpose. The signal can include digital data, analog data, voice, audio, video or anything else that can be in a signal.
The component used to shift signals from lower to higher frequencies or from higher to lower frequencies is called a mixer. A mixer multiplies its signal inputs often producing very complex products in the process. From an input spectrum containing perhaps hundreds of competing signals at a receiver""s antenna, only one of these frequency products should be passed as an output signal. The output signal may go through other filters after the mixer. This one wanted signal may thereafter be amplified, usually by a variable amount of gain. The RF signal can be a transmitted or a received signal. The LO signal is generated locally and selects a certain channel. The channel is certain range of frequencies over which data or information can be transmitted and is used to access the appropriate or desired signal. On the transmitting end, the mixer combines a signal with a carrier wave to produce an outgoing RF signal. The carrier wave is at a frequency in a desired channel. On the receiving end, the mixer combines an incoming RF signal with a LO signal to produce the desired signal.
Furthermore, noise can be introduced into an electronic device by each component added. Every transistor adds some noise to a signal passing through it. The noise affects are cumulative. Thus, noise can be reduced by reducing the number of transistors used in a mixer. Reducing the number of transistors or components used also increases reliability by having less components that can fail.
For the reasons stated above, and for other reasons stated below which will become apparent to those skilled in the art upon reading and understanding the present specification, there is a need in the art for a highly linear, low voltage mixer in wireless applications.
One embodiment of the invention is a mixer having at least one path from a voltage supply to a ground node wherein each path of the at least one path includes no more than two transistors. The mixer comprises a first transistor, a second transistor and a third transistor. The first transistor has a gate, source, and drain. The source is connected to the voltage supply and the gate and the drain are connected to an output node. The second transistor has a gate, source, and drain and the drain is connected to the output node, the source is connected to the ground node, and the gate receives a positive phase of the first signal and a positive phase of the second signal. The third transistor has a gate, source, and drain. The drain is connected to the output node, the source is connected to the ground node, and the gate receives a negative phase of the first signal and a negative phase of the second signal.
Other embodiments of systems and methods are disclosed.